Stitch formation



March 19, 1968 e. B. ARMSTEAD, JR 3,373,706

STITCH FORMATION 4 Sheets- Sheet 1 Filed April 12, 1965' FIGS INVENTOR GEORGE B. ARMSTEAD,JR.

ATTORNEY March 19, 1968 G. a. ARMSTEAD, JR

STITCH FORMATION 4 Sheets-Sheet 2 Filed April 12, 1965 INVENTOR GEORGE B. ARMSTEAD,JR.

'ATTORN EY5 March 19, 1968 G. B. ARMSTEAD, JR 3,373,

STITCH FORMATION 4 Sheets-Sheet 5 Filed April 12, 1965 GEORGE B. ARMSTEAD,JR.

BY J M ATTORNEY March 19, 1968 G. B. ARMSTEAD, JR 3,373,

STITCH FORMATION 4 Sheets-Sheet 4 Filed April 12, 1965 FIGIO ATTORNEY 3,373,706 STITCH FORMATION George B. Armstead, Jr., Glastonbury, onn., assignor to The Merrow Machine Company, Hartford, Comm, a corporation of Connecticut Filed Apr. 12, 1965, Ser. No. 447,158 12 Claims. (Cl. 112-462) ABSTRACT OF THE DTSCLOSURE A chain stitch seam is formed by forming a first sequence of stitches along a line, and simultaneously forming a second sequence of stitches in overlaying relation with, and along the same line as, the first sequence of stitches. The stitches of the second sequence are positioned between the stitches of the first sequence along the length of the seam to give the seam the appearance, coverage, and strength of a seam formed from a single sequence of stitches each of a length one-half the length of the individual stitches of the seam of this invention.

This invention relates to stitch formation, and more particularly to an improved apparatus for, and method of forming an overedge chain stitch seam for assembling parts in the production of sewn items, and to an improved seam formed thereby.

A skilled operator employing a modern high speed sewing machine to form a chain stitch seam can normaliy present material to the machine at a substantially greater rate than can be handled by the sewing machine, so that it is the speed at which the sewing mechanism can be operated which controls the maximum rate of stitch formation. The maximum operating rate of the sewing mechanism is determined, in part, by a number of factors including the maximum permissible stresses in the drive mechanism and the needle and looper mechanism, the stresses in the threads employed to form the stitches, and the noise level of the machine, all of which are adversely affected by an increase in the speed of the machine. Accordingly, while from the production standpoint it is desirable to form the seam at the maximum possible rate, there are certain physical limits beyond which the speed of operation of the machine cannot be advantageously increased.

In the formation of an overedge chain stitch seam on a commercial high speed sewing machine such as the well known Merrow machine, two pieces of work material are fed through the machine in intermittent increments by the machine feed mechanism in superimposed relation, with the edges of the work material to be joined being positioned in vertical alignment. The movement of the feed mechanism is coordinated with movement of a thread carrying needle which passes a loop of thread downwardly through the superimposed pieces of work material during each dwell between feeding increments. A lower looper picks up and retains the loop of thread as the needle is retracted from the work material. When the needle is fully retracted, the feed mechanism is actuated to advance the work material through the machine an increment equal to the length of a single stitch. Simultaneously, the lower looper and an upper looper, driven in coordination with the needle, manipulate the loop of thread to draw the loop outwardly beneath the work material and pass it upward around the edges in position to be interlooped with the next loop carried through the work material by the needle. Alternatively, one, or both of the loopers may carry a cover thread to be interlooped with the needle thread to form a two or three-thread stitch, as desired.

As the movement of the looper mechanisms and the needle actuating mechanism is relatively complex and ited States Patent 3,373,7d6 Patented Mar. 19, 1968 must be closely coordinated, it is apparent that rather severe limitations are imposed on the speed of operation of the stitch forming mechanism. However, it is similarly apparent that the simple reciprocating movement of the feeding mechanism may readily be adjusted to advance the material through the machine in relatively large increments without imposing excessive loads on this mechanism.

From the above, it is apparent that, for any given speed of operation of the stitch forming mechanism, the rate at which the seam is formed and the length of the stitches will vary directly with the length of the feed increment. However, for any given condition, there are certain limitations beyond which the increment of feed cannot be increased as the longer stitches will result in an unsightly seam of poor quality and reduced holding power.

Most modern high speed commercial sewing machines may be employed to form diiferent types of stitches, with the characteristics desired in a particular seam governing the choice of stitch to be employed. However, it has not heretofore been considered practical to form a single seam composed of a combination of stitch types, even though such a combination would greatly increase the possible range of scam characteristics.

It is an object of this invention to produce a chain stitch seam of two separate sequences of aligned stitches.

Another object is to form a chain stitch seam in a piece of work material at an accelerated rate.

Another object is to produce a chain stitch seam composed of two separate sequences of chain stitches, with the stitches in each sequence offset along the length of the scam in relation to the stitches in the other sequence.

Another object is to provide an improved overedge sewing machine capable of forming a chain stitch seam at an increased rate.

Another object is to provide a method of forming a chain stitch seam employing a combination of stitch types.

Other objects and advantages of this invention will become more apparent from the following specification taken with the drawings in which:

FIG. 1 is an end elevation View, with parts broken away, of an improved sewing machine according to the present invention suitable for carrying out the method of this invention;

FIG. 2 is a front view, partially in section, with certain parts broken away or omitted, of the improved machine shown in FIG. 1;

FIG. 3 is a fragmentary section view showing the upper looper and the feed mechanism of the sewing machine shown in FIG. 1; and

FTGS. 4ll are perspective views illustrating selected chain stitch seams which may be formed in accordance with the present invention.

Referring now to the drawings, a sewing machine according to the present invention, indicated generally by the numeral 3, is illustrated in FIGS. 1-3. The sewing machine illustrated and described herein is an improvement over the well-known Merrow overedge sewing machine, details of which are illustrated in US. Patent 2,755,757, granted to Bernard N. Pierce. The machine 3 includes a conventional reciprocating feed mechanism 4 for feeding pieces of work material M1, M2, in intermittent increments through a stitching mechanism. The stitching mechanism includes a first needle 5 mounted for reciprocating movement on a needle carriage 6, a lower looper 7 mounted on a looper carrier 8, and an upper looper 9 mounted on an upper looper carrier 10. Looper carriers 3 and it} are driven in coordination with one another and in coordination with needle carrier 6 by a pair of cylindrical cams 11, 12. The stitch forming mechanism also includes a second needle 13 mounted on needle car- 3 riage 6, a lower looper 14 mounted on looper carrier 8, and an upper looper 15 mounted on looper carrier 10. Since corresponding parts of the stitch forming mechanism are mounted on and driven by common driving elements, exact coordination between these elements is always assured.

As illustrated in FIG. 1, the two needles of the sewing mechanism are mounted in tandem and are spaced from one another along the direction of successive stitch formation so that, as the superimposed layers of work material M1, M2, are fed through the machine, a first sequenee of stitches is formed in the material by the first needle and the associated loopers 7, 9 and a second sequence of stitches is superimposed over the first in exact alignment along the length of the seam by the second needle 13 and its associated loopers 14, 15.

Since two stitches are simultaneously formed through the work material following each increment of feed, the feed increment can be doubled without sacrificing either holding power, or material coverage. However, in order that the seam formed by the two needles and their associated loopers have the appearance of a seam formed by a single needle, it is necessary for the second sequence of stitches to be offset longitudinally along the seam a distance equal to one half of a stitch length, thereby giving the appearance of a single sequence of very short stitches.

To assure that the second formed sequence of stitches is positioned between the stitches of the first formed sequence, the needle spacing must bear a specific relation to the length L of the increment of feed through the machine. This desired stitch spacing is attained by providing a needle spacing equal to one half the length of an increment of feed, or a spacing equal to any whole-number multiple of the length of feed increment plus one half the length of a feed increment. Thus, it becomes apparent that for a particular spacing, the number of stitches per inch may be varied, so long as this desired relation is maintained. For example, with a needle spacing of inch, a feed length L of /1 inch (needle spacing 1 /2 L) will result in 8 stitches per inch with the stitches formed by each needle being equally spaced between successive stitches formed by the other needle. By reducing the feed increment so that the needle spacing is 2 /2 times the feed increment, approximately 13 stitches are produced per inch while the 3 /2 times relation results in approximately 18 stitches per inch.

The length of the feed increment L can readily be varied in the conventional manner by adjustment of the feed mechanism 4. Also, the spacing of the tandem sewing mechanism may be varied by changing the spacing of the needles and adjusting the looper mechanisms accordingly, making any desired stitch length or count possible While maintaining the desired stitch spacing.

Examples of stitches formed in accordance with the present method are illustrated in FIGS. 4-ll. FIG. 4, illustrates a seam of the Federal Standard Type 501 wherein a first sequence of stitches is formed from a single needle thread 23, and a second sequence of stitches formed by a second needle thread 24 is superimposed thereover to produce a seam having all the characteristics of a seam formed from a single sequence of stitches of one half the length of the stitches in the illustrated seam. The tandem seam has an added advantage in that, in use, if a thread is broken the material will be prevented from separating by the other sequence of stitches to thereby prevent raveling of the seam.

' FIG. 5 illustrates second seam formed from two superimposed sequence of stitches of the Federal Standard No. 504 type. In this scam, the first formed sequence of stitches includes a needle thread 25, a lower looper thread 26, and an upper looper thread 27, while the second formed sequence of stitches includes a needle thread 28, a lower looper thread 29, and an upper looper thread 36. FIG. 6 illustrates a seam made up of two superimposed sequence of stitches of different types. The first formed sequence is of the Federal Standard No. 501 type formed from a single thread 31, while the secondforrned sequence of stitches is of the Federal Standard No. 502 type made up of a needle thread 32 and a single looper thread 33.

FIG. 7 illustrates a seam made up of two superimposed sequence of stitches each of the Federal Standard No. 502 type. The first formed sequence is made up of a needle thread 34 and a single looper thread 35, and the second sequence is similarly made up of a single needle thread 35 and a single looper thread 37.

FIG. 8 illustrates a seam joining two pieces of work material M1, M2 and is made up of two separate sequences of stitches each of the Federal Standard No. 503 type and in which the first sequence of stitches includes a needle thread 39 and a looper thread 38 and a second formed sequence including a needle thread 41 and a looper thread 40.

The seam illustrated in FIG. 9 is made up of a first formed sequence of thread of the Federal Standard No. 501 type formed from a single needle thread 42, and a second formed sequence of the Federal Standard No. 504 type made up of a needle thread 43, a lower looper 44, and an upper looper thread 45.

FIG. 10 illustrates a simple crochet seam made up of two sequence of stitches, the first formed sequence being made up from a single needle thread 46, and a second formed sequences made up of a single needle thread 47.

The seam illustrated in FIG. 11 is made up of a variation of the Federal Standard No. 510 type stitch wherein the loops are penetrated by both of the laterally spaced needles. This seam demonstrates that the method according to this invention may be employed to form seams wherein a plurality of laterally spaced needles are employed at each of the longitudinally spaced stitching stations. This seam includes a first formed sequence of stitches made up of a first needle thread 48 and a second needle thread 49. The subsequently formed sequence of stitches is similarly made up by a first needle thread 50 and a second needle thread 51.

The above illustrated seams demonstrate that applicants method and apparatus may be employed to form any of the standard overedge scams or stitches at an accclerated rate, thereby increasing the production rate of an operator and machine Without sacrificing either quality or appearance of the seam. Further, seams made up of a combination of various stitches may readily be formed, as illustrated, thereby increasing the range of scam characteristics available.

What is claimed is:

1. The method of forming a chain stitch seam along a piece of work material which comprises the steps of passing a first needle thread through the work material at points spaced along a line to form a first sequence of chain stitches in the material, and simultaneously passing a second needle thread through the work material at points spaced along the same line and between the points where said first needle thread is passed through the work material to form a second sequence of chain stitches over laying said first sequence of stitches, said first and second sequences of chain stitches cooperating to form a single chain stitch seam.

2. The method of forming a chain stitch seam along a piece of work material which the steps of passing a first needle thread through the work material at spaced points along the seam to form a first sequence of chain stitches each having a length L along the scam, and simultaneously passing a second needle thread through the work material at spaced points along the seam to form a second sequence of chain stitches each having a length equal to the length L of the stitches of said first sequence, said first and second threads being passed through said material along a common line at points spaced from one another, said second sequence of chain stitches overlying said first sequence of chain stitches to form a single chain stitch seam.

3. The method of forming a chain stitch seam along a piece of work material as defined in claim 2 wherein said needle threads are simultaneously passed through the material at points spaced along said common line a distance equal to nL+ /zL where n is any whole number, whereby the stitches formed from each needle thread will be positioned equidistant between the stitches formed from the other needle thread.

4. The method of forming a chain stitch seam as defined in claim 1 wherein the stitches formed by each of the needle threads are of different types to form a seam wherein alternate stitches along the length of the seam are dissimilar.

5. The method of forming a chain stitch seam as defined in claim 1 wherein at least one of said needle threads is interlooped with at least one additional thread.

6. An over-edge chain stitch seam comprising, a first continuous needle thread formed into a series of loops penetrating a piece of work material at longitudinally aligned spaced points along the seam and interlooped to form a first sequence of stitches, and a second continuous needle thread formed into a series of loops penetrating the piece of work material at points between and longitudinally aligned with the points at which the loops of said first needle thread penetrate the work material and interlooped to form a second sequence of stitches spaced between the stitches of said first sequence, said second sequence of stitches overlaying said first sequence of stitches and cooperating therewith to form a single overedge chain stitch seam.

7. An over-edge chain stitch seam according to claim 6 wherein at least one of said needle threads is interlooped with at least one looper thread to form a sequence of multiple thread stitches.

8. An over-edge chain stitch seam according to claim 6 wherein said stitches of said second sequence are spaced along the length of the seam equidistant between the stitches of said first sequence.

9. An over-edge chain stitch seam according to claim 8 wherein the stitches of said first sequence are of a different type from the stitches of said second sequence.

10. An over-edge sewing machine comprising a feed mechanism for feeding work material past a stitch forming station in intermittent increments, a pair of spaced needles, a needle carrier supporting said needles in alignment in the direction of feed of the work material at said stitch forming station, means driving said needle carrier to drive said pair of needles to simultaneously penetrate the work material after each increment of feed, and looper means cooperating with said needles to form an independent sequence of stitches with respective threads carried by said needles with the sequence of stitches formed by the thread carried by one of said needles overlying and cooperating with the sequence of stitches formed by the thread carried by the other of said needles to form a single over-edge seam.

11. An over-edge sewing machine according to claim 10 wherein said intermittent increments of feed each have a predetermined length L and said needle carrier supports said needles in spaced relation to one another along the line of successive stitch formation a distance equal to nL+ /2L where n is any whole number so that stitches formed by each needle will be positioned equidistant in the work piece between the stitches formed by the other needle and in longitudinal alignment therewith along the length of the seam.

12. An over-edge sewing machine according to claim 11 wherein the feed mechanism includes means for varying the length L of the feed increments to vary the value of n to vary the length of stitch formed by each of said needles.

References Cited UNITED STATES PATENTS 2,679,220 5/1954 Biesemeyer et al 112-215 2,834,309 5/1958 Russell et al. 112163 2,973,730 3/1961 Schweda et al. 112162 3,246,620 4/1966 Sigoda et al. 1l2162 JORDAN FRANKLIN, Primary Examiner. I. BOLER, Examiner. 

